Dr.PeteFamMed said:

Keep the original post as written when you update it, and add the correction underneath.

Thank you — that is the clearest version of this I have read, and I have read a lot of them. Taking it to my next appointment.

Clinical perspective, offered as context rather than as advice. The useful move here is to separate what is established from what is widely repeated. Those two sets overlap less than the confident tone of most write-ups suggests, and the second set is where nearly all the disagreement on this board comes from.

Found this through search years later and it is still the best discussion of the question, so adding one thing. One practical note: write down what you did and when, before you need it. Reconstructing a timeline from memory three months later is how people end up unable to answer the one question that would have resolved it.

Reporting back.

Update, and it is the boring outcome: nothing was wrong. The measurement I was reading had moved less than its own week-to-week variation, which somebody said upthread and I did not believe.

Adding the numbers, since they settle part of this. For anyone reading later: the numbers in this thread are worth checking against a primary source before you act on them, including mine. Half the figures circulating in this community trace back to a secondary summary that dropped a qualifier.